A droplet actuator typically includes one or more substrates configured to form a surface or gap for conducting droplet operations. The one or more substrates establish a droplet operations surface or gap for conducting droplet operations and may also include electrodes arranged to conduct the droplet operations. The droplet operations substrate or the gap between the substrates may be coated or filled with a filler fluid that is immiscible with the liquid that forms the droplets. It can be difficult to control the size and volume of droplets dispensed in a droplet actuator. There is a need for new approaches to accurately dispensing droplets in a droplet actuator.